42 MODEL AVIATION
BY MICHAEL RAMSEY
Park View: Maxford USA Curtiss Jenny Electric ARF
“IT’S ABOUT TIME somebody made a
practical model of the Curtiss Jenny” is what I
thought when I saw the Green Models
rendition parked humbly at the Maxford USA
booth display table during the 2006 AMA
Convention. I stopped by repeatedly to absorb
the ARF’s fine craftsmanship and the amount
of scale detail that was included on such a
small model.
I mean, this was a knock-around park
flyer—not a museum-scale aircraft. The only
things that made this Jenny different in detail
from a Scale Masters model were the size and
the curious transparent orange covering. I’m
exaggerating, but not much; all this model
needs is a dummy engine and a pair of pilot
busts to make any JN-4 Standard fan do a
double take.
Maxford has raised the bar in scale
ARF park flyers.
As was the
Colorful Butterfly I
reviewed in the
August 2006 MA, the
Jenny is a pleasure
to admire when
it’s just sitting
still. After looking
at it for a while, the
transparent covering actually added
appeal; the clear view of the elegant
framework and craftsmanship
enhanced the model, giving an old classic even
more character.
When I brought the Jenny home from the
Convention, a finished instruction manual
wasn’t available yet (but was soon posted
online). The kit now comes with a full manual.
Just a few pages of pictures numbering the
steps to make the model flight ready were
provided.
The nice surprise after inspecting all the
contents was finding that not only were the
semisymmetrical wings built as one piece, but
they were assembled with the eight plywood
struts bolted in place and laced with
monofilament thread that crisscrossed the
wings through stainless-steel turnbuckles and
neatly tied off at either end to lightweight
springs.
Before unfolding
the wings and
calling the
assembly
finished I added
the two
aileron
servos with a 12-
inch extension on each so
they could be connected to the receiver
that would be installed under the forward
passenger’s cockpit. Any 4- to 6-gram servo is
more than adequate to move the prehinged
ailerons. I set up the linkage to provide
maximum surface deflection.
I was tempted to tighten the strut screws
and 2mm hex nuts right away, but thought I
better save that job for when the wings were
installed on the fuselage.
My model’s covering needed very little
wrinkle shooting. I used a trim-seal tool to do
the job because I was afraid a heat gun might
stretch or cause the rigging to break. After
handling the model clumsily, I found that the
rigging was forgiving when plucked or
shocked by accident.
The prehinged tail surfaces were rigged as
well and set up for pull-pull control—just like
on the full-scale Jenny! The vertical fin’s
plywood tabs simply recessed into notches that
were laser cut into the horizontal stabilizer.
Those tabs keyed to notches in the stabilizer
platform on the fuselage. Then, from
underneath, long 2mm screws fed
through the fuselage, into the tabs
on the fin, and then back outside, to
be locked in place with 2mm nuts
with washers. I recommend Loctite
here. The pull-pull cables for the tail
surfaces were already installed on my
model.
Because the inside of the fuselage was too
cramped for my hands, I installed the servos to
the fishing-tackle ends on the cables. Then
with the servos under power from the radio, I
could lead the cables through the control
surfaces and tension them without moving the
servo arm by accident.
Rudder control was the easiest to set up.
The elevators were a bit tricky because each
half was independently linked. Tensioning the
cables to where both elevators were equal at
the neutral point was the only challenge of the
build.
Instead of tying a knot in the connecting
spring, I threaded the cable through a small
piece of heat-shrink tubing à la the swag
fittings used on larger scale pull-pull
07sig2.QXD 5/23/07 10:58 AM Page 42
Photos by the author and Mark Lanterman
Assembled motor mounts are included to suit gearbox and
direct-drive outrunner installations. They simply bolt on.
The battery hatch securely clips in place. Four 4mm nylon wing
bolts also secure the scale landing gear.
Notice the carbon-fiber LE and turtledeck spine. The hardware package has matching
covering for repairs.
The control surfaces are installed at the factory with film covering for hinges. The pullpull
control matches that of the full-scale aircraft.
Motor: Feigao 20mm 4200 kV/6.6:1
gearbox
Battery: E-Tec 700 mAh 3S
Propeller: 9 x 6 SF (included)
Motor current: 8.3-amp peak draw
Motor output: Highest 108 watts
Radio system: Polk’s Hobby Tracker III
transmitter, Berg 4L receiver, two Blue
Arrow BA-TS-4.3 microservos, two S75
servos, two 12-inch extensions, one Y
harness, Thunderbird-9 ESC
Ready-to-fly weight: 16 ounces
Flight duration: Eight to 10 minutes
Test-Model Details
Tension of the rigging is maintained by a
spring on each end of the lines. The struts
are painted light plywood.
July 2007 43
07sig2.QXD 5/23/07 11:50 AM Page 43
44 MODEL AVIATION
+
• Lightweight, well engineered, well built.
• Flying wires just like full scale, and all
preinstalled.
• No glue required.
• Bolt-on motor-mount options for
gearbox or direct drive.
-• Landing gear loosens easily. (Newest
releases have been fixed.)
• Inadequate cooling for power system.
(Easy to fix.)
Pluses and Minuses
Consider the Jenny a slow flyer because of its high-drag airframe. A new version is
available in opaque yellow.
Type: Semiscale ARF
Pilot skill level: Intermediate
Wingspan: 38 inches
Wing area: 287 square inches
Length: 23.5 inches
Weight: 17 ounces
Wing loading: 8.2 ounces/square foot
Power (recommended): Speed 390
motor geared 6:1, 2S-3S Li-Poly battery
Radio: Four channels (minimum), four
microservos
Construction: Laser-cut balsa, light
plywood
Covering/finish: Transparent orange film
Price: $135.99
Specifications applications. Instead of “crimping,” I added
a drop of thick cyanoacrylate with the cable
pulled taut. If the elevators come out
somewhat uneven when you do this,
disconnect the long cable and tie enough
knots in the line to shorten the string and
correct its length.
Two motor mounts were included to suit
either a gearbox or a brushless outrunner
motor. Each plywood laser-cut mount tab
locked into the firewall and was secured
with two small screws.
The instructions showed a brushed Speed
350 motor and 6:1 gearbox. I had an older
foamie power system laying around that had
an output of 80-100 watts, depending on
whether a two- or three-cell battery was
chosen. It would use the included 9 x 6 SF
propeller and provide the necessary ground
clearance. My amp draw is approximately 8
amps (wide-open throttle) static with this
setup.
The firewall required light carving to
allow the Thunderbird-9 controller to pass
through. I fit the cowl so it was tight on
three sides but open on the bottom, to allow
heat from the motor to escape.
To mount the finished fuselage I fed it,
back to front, between the wings and onto
the corresponding frame of the lower centersection.
As the center cabane mounting tabs
met the struts in the fuselage, the assembly
had to be sort of carefully jiggled into place.
It was a thing of beauty when the whole
assembly fit together snugly. The quality
and accuracy of the parts fit left me with no
alignment issues or curiously shaped gaps to
try to fix or ignore.
I used all the hardware that came with
the kit. The only part that didn’t work out
was the carbon-fiber rod included as either
pushrods or wingtip skids. I used the Z-bend
finished metal pushrods for the ailerons, so I
attempted to bend the 1mm carbon rod and
fit it into the plywood bracket holes in the
bottom of the lower wingtips.
Carbon fiber is well known for its
stiffness, and I couldn’t get the skid material
to work. I substituted music wire of the
same diameter and had much more luck.
Don’t skip this scale detail; the narrow
wheelbase permits regular tip-dragging
landing.
The landing gear was last to attach, as it
was secured with the same screws that held
on the bottom wing. The wheels had plastic
tubing for wheel collars. I suggest carefully
gluing that tubing in place with
cyanoacrylate.
My Jenny balanced on the tail-heavy
side of the CG range. Knowing that I’d
want authority to keep the model from
nosing over while on the ground, I left it in
that balance condition. The wing loading
and power-to-weight ratio had me confident
that this Jenny could muscle through any
poor flight attributes of a tail-heavy aircraft.
Flying: This is one of the first park flyers
I’ve owned that had as much scale detail as
a Giant Scale model. Rigging and control
cables litter the outside. Despite the welldesigned
wooden framework and carbon
fiber on the LE of the wings and turtledeck
spine, this airplane should be handled with
care. I carry it around by the midsection of
the top wing.
The Jenny’s overall size permits it to be
left assembled for travel. Besides, removing
the fuselage from the wing assembly is a
cumbersome process involving tiny screws
I’d hate to lose.
At one point I was disappointed to find
that a hole was made in the bottom of the
lower wing. This is when I truly appreciated
Maxford USA’s foresight to include a patch
of matching covering.
With its balloon-shaped foam wheels,
the Jenny will fly from short grass. On
takeoff the oversized tail surfaces gain
instantaneous authority, and keeping the
model straight and in a smooth climb is
easy. Even though they are hiding on the
top ends of the wing, the ailerons are quite
effective as well.
Don’t expect this model to fly fast. The
100-watt motor system provides plenty of
pull for aggressive climbs, but drag of the
wires and high-aspect-ratio wings is a lot to
overcome. However, all that adds to the
Jenny’s charm. It’s a slow, lazy model that
did everything I told it to, as long as it
wasn’t related to IMAC (International
Miniature Aerobatic Club) or 3-D.
Having maximum throws in the control
surfaces was comforting, except with the
elevator when full input produced a highspeed
tip stall. Inside 25° of elevator
deflection the Jenny is a forgiving flier with
straight-ahead stalls.
At slow speeds it’s fun to just putt-putt
around and steer using only the rudder. Here
the aircraft appreciated full rudder throw
and showed only small down-pitch coupling
in the nose at full input.
High rate on the ailerons was nice to
have as well because it allowed the Jenny to
roll at rates that are typical of a 40-size
trainer. That means it can Point Roll if the
07sig2.QXD 5/23/07 10:58 AM Page 44
pilot is adept at mixing in rudder and
elevator during the maneuver sequence.
Inverted flight is possible, but that’s not so
Jennylike.
Landings were smoothest if a little power
were carried all the way to touchdown. The
extra thrust is again required to overcome
the drag of all those cables. (The full-scale
Jenny was the same way.)
To prevent ground looping, touch the
main wheels down while holding the model
at a nose-high attitude. As soon as that fixed
tail skid touches the ground, the model stops
quickly and nosing over is no longer
possible.
The power combination in my model
allows for a 10-minute flight. However, the
battery is warmer than I would like at the
end since only half throttle is used during
the flight. To promote the flow of heat to the
outside, I opened up the covering on the
battery hatch.
The complex landing-gear assembly is a
great feature. But the contact arrangement
with the mounting screws allows the gear’s
front end to come loose from time to time no
matter how tight the screws are.
The system would work better if the
relief bends in front of the wire pointed
backward instead of forward. That way the
mounting points would be in tension and
little force from the mounting screws would
be required to hold the gear in place. I’ll fix
my gear by silver-soldering a wire that
encloses the front mounting holes.
I’m proud to own this Jenny for its flying
qualities and distinctive features. I’ve flown
it in winds as high as 10 mph with no
problems.
To add a spinner to the front end, I
recommend the prop nuts available from
Du-Bro Products. Maxford USA just
announced the release of this Jenny covered
in opaque yellow “fabric-like” covering. The
last touch to my Jenny might be to add a pair
of lightweight pilots. MA
Michael Ramsey
[email protected]
Manufacturer/Distributor:
Maxford USA Corp.
DBA of Green RC Models USA
13909 Artesia Blvd.
Cerritos CA 90703
(866) 706-8288
www.maxfordusa.com
Sources:
Accessories:
Du-Bro
80 Bonner Rd.
Wauconda IL 60084
(800) 848-9411
[email protected]
www.dubro.com
Berg 4L receiver, Thunderbird-9 ESC:
Castle Creations
235 S. Kansas Ave.
Olathe KS 66061
(913) 390-6939
[email protected]
www.castlecreations.com
Blue Arrow BA-TS-4.3 microservos:
AeroMicro
2090 Duane Ave.
Santa Clara CA 95054
(408) 496-6699
[email protected]
www.aeromicro.com
Feigao 20mm, 4200 kV motor; GWS 350-D
gearbox; 700 mAh E-Tec Li-Poly, 11.1-volt
battery:
BP Hobbies
140 Ethel Rd. W. Suite J
Piscataway NJ 08854
(732) 287-3933 (9 a.m.-5 p.m. EST)
[email protected]
www.bphobbies.com
Spektrum RC S75 servos:
Horizon Hobby, Inc.
4105 Fieldstone Rd.
Champaign IL 61822
(217) 352-1913
www.spektrumrc.com
Tracker III transmitter:
Polk’s Hobby
698 S. 21st St.
Irvington NJ 07111
(973) 351-9800
[email protected]
www.polkshobby.com
Other Reviews of This Product:
May 2007 Fly RC magazine: page 90
March 2007